tornado core

The tornado core is a concentrated, swirling column of air that extends downward from a mesocyclone, which is a rotating column of air within a thunderstorm. This core is typically no more than one kilometer in diameter and forms where the thunderstorm's updraft and downdraft meet.1

As the core approaches the ground, surface friction limits airflow, reducing pressure within the core. This pressure drop causes moisture in the air to condense, forming a visible condensation funnel, which gives the tornado its characteristic shape. The core is surrounded by a region of lower atmospheric pressure bounded by the strongest winds. While most tornadoes rotate cyclonically (counterclockwise in the Northern Hemisphere), about 5% rotate anticyclonically. Extreme wind speeds, sometimes exceeding 300 mph, can occur in the corner region where air rushes into the core.123